(a) Field of the Invention
The present invention relates to thin film transistor array panels for a liquid crystal display and the methods for manufacturing the same.
(b) Description of the Related Art
A liquid crystal display (LCD) is one of the most popular flat panel displays (FPDs). The liquid crystal display has two panels having electrodes for generating electric fields and a liquid crystal layer interposed therebetween.
The transmittance of incident light is controlled by realigning the liquid crystal molecules of the LCD, as the intensity of the electric field applied to the liquid crystal layer changes.
In the most widely used liquid crystal display, the field-generating electrodes are provided at both panels, with one of the panels having switching elements such as thin film transistors and pixel electrodes, and the other panel having color filters and black matrix.
In general, a thin film transistor array panel is manufactured by a photolithography process using photoresist pattern as an etch mask. However, the misalignment of interlayes in fabricating a multi-layered structure negatively affects display characteristics of the LCD. To solve this problem, it is desirable that an alignment key of an opaque material is formed of the same layer as the lowest layer of the thin film patterns.
On the other hand, it is important to increase an aperture ratio of the thin film transistor panels of LCD to improve a brightness of LCD. However, the LCD has several obstacles in reducing the aperture ratio of the thin film transistor. Firstly, a certain distance between the pixel electrode and the data line must be maintained in order to avoid the parasitic capacitance generated therebetween by coupling effects. Secondly, a black matrix must be wide enough to cover a possible misalignment of the two panels. To solve these problems, several methods have been suggested. One suggests an insulating layer interposed between the pixel electrode and the data line and made of organic material having a low dielectric constant. The other suggests color filters formed on the same panel having thin film transistors.
However, the latter case is economically unsound. Because the color filters are formed after more expensive processes of forming thin film transistor, the failure in the color filter formation process wastes a lot of resources and increases the manufacturing costs. On the other hand, the former method cannot generate enough storage capacitance between the gate line and the pixel electrode.
It is therefore an object of the present invention to provide a thin film transistor array panel for a liquid crystal display and methods for manufacturing the same, minimizing misalignment problems between two panels of an LCD and increasing its aperture.
It is another object of the present invention to provide a thin film transistor array panel for a liquid crystal display and methods for manufacturing the same with yield imrovements.
It is another object of the present invention to simplify manufacturing methods of a thin film transistor array panel for a liquid crystal display.
It is therefore an object of the present invention to provide a thin film transistor array panel for a liquid crystal display and methods for manufacturing the same minimizing parasitic capacitance and having enough storage capacitance.
These and other objects are provided, according to the present invention, by forming a thin film transistor after forming color filters, forming black matrix having an opening portion at pixel under the color filters, and forming an alignment key for inter-layer alignment when forming the color filters and the black matrix.
Here pads, which transmit a signal from an external circuit to a signal wire, or a common wire to apply a common voltage are formed when forming the black matrix.
These and other objects are provided, according to the present invention, by using a data line as the light-block layer blocking the light incident to the thin film transistor by forming the data line under the color filters, and together forming a semiconductor pattern and contact hole by using a photoresist pattern having different thickness depending on the positions of an etch mask to simplify manufacturing methods of thin film transistor array panels for liquid crystal displays.
In a thin film transistor array panel for a liquid crystal display according to the present invention, a black matrix having an opening at pixels of matrix array is formed on the display area of an insulating substrate including a display area, a peripheral area at the circumference of the display area, and outer area except for the display area, and the peripheral area. Red, blue and green color filters are formed at the pixels on the insulating substrate, and an insulating layer covering the black matrix and the color filters is formed. A gate wire including a gate line and a gate electrode connected to the gate line is formed on the insulating layer, and a gate insulating layer covering the gate wire is formed on the insulating layer. A semiconductor pattern and ohmic contact layers are sequentially formed on the gate insulating layer, and a data wire including a source electrode and a drain electrode which are made of a same layer on the ohmic contact layers and separated from each other, and a data line connected to the source electrode and defining the pixels with matrix array by crossing the gate line. A passivation layer covering the data wire and having a first contact hole exposing the drain electrode is formed, and a pixel wire including a pixel electrode connected to the drain electrode through the first contact hole.
An alignment key may be formed with the same layer as the black matrix or the color filters of the outer area.
A common wire including common signal line transmitting common signal to common electrode opposing the pixel electrode and common pads transmitting the common signal to the common signal line from external circuits and connected to the common signal line may be formed with the same layer as the black matrix.
The gate wire further includes a gate pad, which is connected to and receives a signal from an external circuit, and the data wire further includes a data pad, which is connected to and receives a signal from an external circuit. The gate pad or the data pad may be formed with the same layer as the black matrix, the gate wire, or the data wire on the peripheral area.
It is desirable that the edge portions of the red, green and blue color filters overlap the portion of the black matrix, and the insulating layer is made of organic insulator material.
In another thin film transistor array panel for a liquid crystal display comprising, according to the present invention, a data wire including a data line is formed on an insulating substrate, and red, blue and green color filters are formed at the pixels on the insulating substrate. A gate wire including a gate line defining the pixel by crossing the data line and a gate electrode connected to the gate line is formed on the insulating layer covering the data wire and the color filters. A semiconductor pattern and ohmic contact layers sequentially formed on a gate insulating layer covering the gate wire and having a first contact hole exposing the data line along with the insulating layer, and a pixel wire including a source electrode connected to the data line through the first contact hole and a drain electrode, which are made of a same layer on the semiconductor pattern and separated from each other, and a pixel electrode connected to the drain electrode is formed on the gate insulating layer of pixels.
The edges of the red, green and blue color filters overlap the edges of the data line, and the insulating layer may be made of organic insulating material having low dielectric consent less than 3.0 and being able to be coated with the thickness of more than 1. The ohmic contact layers may be formed of doped microcrystallized amorphous silicon, silicide of metal or doped microcrystallized amorphous silicon.
The data wire may have a light blocking layer to block the light leakage between pixels. A passivation layer covering at least the semiconductor pattern between the source electrode and the drain electrode may be formed, and a colored organic layer may be formed on the passivation layer. It is desirable that the colored organic layer is made of photosensitive organic insulating material including black resin, and used as a spacer between two panels.
In a method for manufacturing a thin film transistor array panel for a liquid crystal display, a data wire including a data line is formed on an insulating substrate, and red, blue and green color filters are formed at the pixels. Next, a gate wire including a gate line and a gate electrode is formed on an insulating layer covering the data wire and the color filters, and a gate insulating layer covering the gate wire is formed on the insulating layer. Semiconductor pattern ohmic contact layers are formed on and at the same time patterning the insulating layer and the gate insulating layer to form a first contact hole exposing the data line. Then, a pixel wire including a source electrode and a drain electrode on the ohmic contact layers, which are made of a same layer as the semiconductor pattern and separated from each other, and a pixel electrode connected to the drain electrode is formed on the pixels.
It is desirable that the first contact hole, the ohmic contact layer and the semiconductor layer are patterned through photolithography process using one mask.
It is desirable that the black matrix, the gate wire, or the data wire have single-layered structure be made of aluminum, aluminum alloy, copper or copper alloy, or multi-layered structure including a conductive material of chromium, molybdenum, molybdenum alloy, chromium nitride or molybdenum nitride.
Also, a redundant gate pad and a redundant data pad respectively connected to the gate pad and data pad may be formed with the same layer as the pixel electrode.